Blind riveting apparatus

ABSTRACT

The disclosure relates to a blind riveting machine of the type including a pull-through mandrel having an enlarged head which is pulled through tubular rivets in succession to expand and place the rivets. The tail end of the mandrel is gripped by two pairs of jaws spaced apart along the mandrel. The pairs of jaws are opened successively, but not both at the same time, so that rivets can be fed, one at a time, past each pair of jaws in succession, whilst the mandrel remains gripped by at least one of the pairs of jaws.

United States Patent Prosser et al.

[ Feb. 20, 1973 54] BLIND RIVETING APPARATUS 2,401,724 6/1946 Dowdle ..72/391 [75] lnventors: Paul Edward Prosser, Hemel Hempstead; John Stewart Sanders; Donald 3557'597 "1971 5 "72/391 Sta ey Sa age, both of S Albans; p f ggi t zggg gr Har- Primary Examiner-Richard J. Herbst pe g Assistant ExaminerGene P. Crosby [73] Assignee: Aerpat A.G. Attorneyl(emon, Palmer & Estabrook [22] Filed: Aug. 19, 1971 ABSTRACT [21] Appl. No.: 173,092

The disclosure relates to a blmd riveting machine of Fm'elgn Apphcauon Pnomy Data the type including a pull-through mandrel having an enlarged head which is pulled through tubular rivets in Sept. 16, 1968 Great Brltaln ..43,859/68 succession to expand and place the rivets- The tail end 521 US. Cl. ..72 391, 72/424, 227/55, mandrel gmped by "9 Jaws Space:

227,114 apart along the mandrel. The pairs of aws are opene [51] Int. Cl. B2" /10 successively, but not both at the same time, so that 581 Field of Search ..72/391, 453, 424; 227/55, 114, 9 a Jaws 227,115, H6, H7 118; 29/243'53, 243.54 m succession, whilstthe mandrel remams gripped by at least one of the pairs of aws. [56] References Cited 14 Claims, 21 Drawing Figures UNITED STATES PATENTS 2,340,066 1/1944 Lee ..72/391 1 195 "Tl 06 ,/55 a e? 495 I53 '/67 /s/ 117 /62 /65 a L- a 19/ 7 8 g {5 53 59 96 /05 9-7 9? 7 7 9? /04- 69 l0 /0/-\ ji 1* y Y so PATENTEBFEBZOISH 3.717 sum DlUF 1 Pmmmrmzd a gjizbz SHEET OZUF 12 sum 10 0F 1 BLIND RIVETING APPARATUS The invention relates to blind riveting apparatus.

In particular it relates to blind riveting apparatus of the type comprising an elongated mandrel having an enlarged head which mandrel in use carries a plurality of tubular rivets, the mandrel head being pulled through successive rivets in turn thereby'to expand the rivet and to effect blind placing thereof in an aperture in a work-piece. Riveting apparatus of this type will hereinafter be referred to as riveting apparatus of the type defined. Such riveting apparatus and the riveting which it carries out are termed blind since access is required to one side only of the workpiece. An example of such blind riveting apparatus and blind rivets for use therewith is that commercially available under the Registered Trade Mark CHOBERT.

The invention provides riveting apparatus of the type defined, including: a plurality of retractable gripping means for gripping the mandrel to pull it through successive rivets as aforesaid, the said gripping means being arranged to grip the mandrel at positions spaced apart along the length thereof; and means for successively retracting from the mandrel each of the gripping means in turn; the arrangement being such that a rivet may be fed on to the mandrel from the tail end thereof remote from the mandrel head and along the mandrel, past the gripping position of each gripping means whilst the latter is retracted, while the mandrel remains gripped, at any one instant, by at least one of the gripping means, different gripping means gripping the mandrel successively at different times.

Conveniently the gripping means are arranged to grip the mandrel at positions near the end thereof away from the head. There may be only two gripping means. Each gripping means may comprise a plurality of jaws (in a preferred form of the invention, two jaws) which are urged together to grip the mandrel between them.

It may be that at least one of the gripping means includes resilient urging means urging it either to grip, or to retract from, the mandrel, and that the apparatus also includes override means for overriding the resilient urging means and positively driving the gripping means to retract from, or to grip, the mandrel. It may be that one of the gripping means includes such resilient urging means urging it to grip the mandrel, and another of the, or the other, gripping means includes such resilient urging means urging it to retract from the mandrel.

The apparatus may include rivet transfer means for transferring rivets in succession from a rivet supplying device onto the aforesaid tail end of the mandrel. It may be that the rivet transfer means is also arranged to convey rivets in succession along the mandrel past at least one, and preferably both, or all the gripping means. It may be arranged that the arrival of the rivet transfer means at a gripping means actuates retraction of the gripping means. Where the said gripping means includes resilient urging means urging it to grip the mandrel as aforesaid, the override means for overriding the resilient urging means may comprise the rivet transfer means. Conveniently the rivet transfer means repeatedly transfers as aforesaid one rivet at a time.

A specific embodiment of the invention, and a modification thereof, will now be described by way of example and with reference to the accompanying drawings, in which:

FIG. 1 is a block schematic diagram illustrating a continuous feed blind riveting machine including control gear and rivet feeding means;

FIG. 2 is an exterior view of the riveting head of the machine;

FIG. 3 is a longitudinal axial section, on the line III III of FIG. 4, through the riveting head at the start of a riveting cycle;

FIG. 4 is a cross-section on the line IV IV of FIG.

FIG. 5 is a longitudinal axial section on the line V V of FIGS. 3 and 4, in a plane perpendicular to that of FIG. 3;

FIGS. 6 and 7 are similar sections to FIG. 3 but showing the riveting head at two successive stages in the riveting cycle;

FIG. 8 is a cross-section on the line VIII VIII of FIG. 7;

FIG. 9 is a section on the line IX IX of FIG. 8;

FIG. 10 is an elevation of the mandrel;

FIG. 11 is a plan view of the member forming a major part of the rivet transfer means;

FIG. 12 is a longitudinal section on the line XII XII ofFIG. ll;

FIG. 13 is an end elevation in the direction of arrow XIII in FIG. 11;

FIGS. 14 and 15 are two different elevations, at right angles to each other, of a member forming an auxiliary part of the rivet transfer means;

FIGS. 16 and 17 are two different elevations, at right angles to each other, of a jaw forming part of one of the gripping means;

FIG. 18 is an elevation of a jaw forming part of the second gripping means;

FIG. 19 is a section on the line XIX XIX of FIG.

FIG. 20 is a block schematic diagram of the control gear of the riveting machine;

FIG. 21 is a sectional view, corresponding to part of FIG. 6, of a modification of part of the riveting head.

The continuous feed riveting tool of this example is shown schematically in FIG. 1, its main components being a blind riveting head 21, a vibratory hopper 22 for storing and supplying rivets, and a control box 23 housing control gear for the riveting head and a feed control 24 for the hopper. The riveting head 21 in this example is aligned in a vertical position (so that it places blind rivets in a suitable workpiece from above) and is mounted in a solid steel frame 25 which is secured to a suitable rigid support 26. The hopper 22 is arranged to supply a succession of rivets to the upper end of the riveting head. The rivets are fed by the vibratory hopper along a horizontal channel or flight 27, at the end of which they fall down a flexible feed tube 28. Intermediate the end of the feed tube 28 is provided an air pusher 29. The air pusher provides a high velocity blast of air along part of the interior of the feed tube in the direction in which the rivets travel along the tube, in order to assist the passage of the rivet along the tube. To this end compressed air is fed into the air pusher through an upper inlet 31, and escapes from the air pusher through a lower outlet 32. The lowermost end of the feed tube 28 connects with the top end of the riveting head.

The blind rivets which the machine of this example is designed to use are those commercially available under the Registered Trade Mark CHOBERT. Each rivet consists of a tubular shank with an enlarged headat one end and with the internal bore of the shank tapering to a reduced internal diameter at the other end. A number of rivets are positioned on a mandrel on which the rivets are a sliding fit. The mandrel has an enlarged head at one end, and the rivets are positioned in the mandrel with their tail ends facing towards the mandrel head. When the mandrel head is pulled through the rivet nearest it, the tail end of the rivet is expanded, thus placing the rivet. Such rivets, and their blind placing by means of a mandrel with an enlarged head, are well known to those skilled in the art of blind riveting.

The vibratory hopper 22 and flight 27 are arranged to supply a succession of rivets into the feed tube 28 so that each rivet has its head end uppermost and its tail end lowermost, so that each rivet arrives at the top of the riveting head with its tail end first.

The riveting head 21 is operated pneumatically, and the control gear in the control box 23 is also operated pneumatically. Compressed air is fed to the control box through a compressed air supply line 33, and pneumatic power actuation of the riveting head from the control gear is achieved by means of four high pressure air lines 34, 35, 36 and 37. The riveting head is also connected to the control gear by means of a number of low pressure air lines, indicated in FIG. 1 collectively at 38. These low pressure air lines carry air signals from the riveting head to the control gear, in a way which will be later described with reference to FIG. 20. Low pressure air supply to the control box is by means of a low pressure air inlet 39.

The riveting head mounting frame 25 comprises a main vertical member 41, having secured to it at its bottom end a transversely extending bottom bracket 42, and at the upper end a top bracket 43 which also extends transversely, above the bottom bracket 42. The bottom bracket'42 is formed with a vertically aligned cylindrical hole 44 through it, which is connected with one free edge of the bottom bracket by a slot 45, across which passes a clamp bolt 46. The bore 44, slot 45 and clamp bolt 46 provide a split clamp which securely holds the main barrel of the riveting head.

The mandrel 40 is illustrated in FIG. and, as mentioned previously, comprises an elongated cylindrical shank 47 having at one end an enlarged cylindrical head 48 which tapers into the shank by means of a tapered portion 49. The free end of the mandrel head is also partially tapered by means of a frusto-conical head end portion 51. The end of the mandrel shank remote from the head has a tapered end 52, and the portion of the shank adjacent to that end is formed with a plurality of small V-section grooves 53 to facilitate gripping of the end of the mandrel by the jaws of the riveting head.

The riveting head has a central cylindrical tubular barrel 54 which is secured in a vertical position in the split clamp in the bottom bracket 42 of the mounting frame, The lowermost end of the barrel carries a riveting nose which is similar to that well known in conventional CHOBERT riveting guns. The riveting nose comprises a nose piece body 55 which is screwed on to the lowermost end of the barrel 54. The bottom end of the nose piece 55 carries a pair of generally semi-cylindrical riveting jaws 56 and 57. Each jaw can pivot outwardly about its rear end and the jaws are spring-urged together. The lowermost or head end of the mandrel can extend through the jaws and a rivet can be pushed tail first outwardly through the jaws so that the jaws close behind it, their outer ends providing an anvil to abut the head end of the rivet whilst the head of the mandrel is pulled through the rivet. The jaws and their springs are such that the weight of a vertical column of rivets on the mandrel is insufficient to force the leading rivet through the placing jaws, which can only be achieved by an additional driving force applied to the uppermost rivet of the column. The construction and operation of such riveting jaws is well known to those skilled in the art of blind riveting, and will not be described further in the present specification.

The riveting head of this example is provided with two pairs of mandrel-gripping jaws, an upper pair 58 and a lower pair 59. The way in which these jaws are mounted for alternate gripping of and retraction from the mandrel, and are reciprocated in order to repeatedly retract the mandrel head through successive rivets, will now be described.

Both pairs of jaws are carried by a jaw carrier which is indicated generally at 61. The jaw carrier 61 is mounted for vertical reciprocating sliding movement on the upper part of the barrel 54 above the lower bracket 42. The jaw carrier 61 has a generally cylindrical symmetry about a central axis along which the mandrel 40 lies. Its lowermost part 62 is formed with a relatively large diameter internal bore which has its lower end closed by an annular plug 63 to form a cylinder 64. Working within the cylinder 64 is a piston 65 formed by an annular flange secured to the barrel 54. The part of the jaw carrier cylinder below the barrel piston 65 is provided with a compressed air connector 66 to which is connected one end of the high pressure air line 34. Likewise the part of the jaw carrier cylinder 64 above the barrel piston 65 is provided with a compressed air connector 67 which receives one end of the high pressure air line 35. The jaw carrier 61 is reciprocable vertically on the barrel 54 to an extent determined by the abutment of the top or bottom wall of the cylinder with the barrel piston 65.

To prevent the jaw carrier 61 rotating about its vertical axis on the barrel, it is provided with a radially extending spigot 68 which is a sliding fit in a vertical slot 69 in the main member 41 of the mounting bracket.

The upper part of the jaw carrier 61 is of reduced diameter to form an upwardly extending central boss 71. Towards the upper end of this boss are mounted the upper jaws 58 and lower jaws 59. The two jaws of each pair are diametrically opposed to each other and each jaw can reciprocate in a direction radial to the axis of the jaw carrier in a suitable bore machined in the jaw carrier. The upper jaws 58 are spring-urged towards each other into the gripping position. One of the upper jaws is shown in greater detail in FIGS. 16 and 17. It has an end face 72 in which is provided a serrated groove 73 of ninety degrees included angle in which one half of the shank of the mandrel is received when the jaw is in its gripping position. Adjacent to the gripping face is an inclined face 74, at one end of which the V-groove 73 opens. The main body portion 75 of the jaw is generally cylindrical and has a step 76 cut out of one side, and a slot 77 in alignment with the V-groove 73. The jaw also has an elongated stem 78. The other jaw of the pair is a mirror image of the one illustrated in FIGS. 16 and 17. As illustrated in FIG. 3, the two upper jaws 79, 81 are mounted so that their two end faces 72 face each other, the jaw 79 being positioned at one end of a transverse cylindrical bore 82 which extends nearly through the upper end of the jaw carrier boss, and the other upper jaw 81 being mounted in the other half of the bore. The two jaws are positioned so that their two end faces 72 are facing each other, and so that the V-section grooves 73 are superimposed. The two inclined faces 74 face upwardly, i.e. towards the tail end of the mandrel. Each jaw is prevented from rotating in the bore 82 by means of a suitable key engaging with the slot 77 in each jaw. The two jaws are urged together into the gripping position by means of two helical compression springs 83, one surrounding the stem 78 of each jaw and acting between the main body 75 of the jaw and one end wall of the bore 82. The outermost end of each jaw stem 78 is threaded and projects outside of the jaw carrier boss. Two locknuts 84 are provided in order to accurately determine the extent to which the jaw can move inwardly towards the other jaw. When the jaws are in the gripping position, the grooved tail end portion of the mandrel shank is gripped between the two opposed V- section grooves 73. The upper jaws can be positively urged apart by an overriding means in the form of a suitable tapered abutment member driven between the jaws to strike the two inclined faces 74 and force the jaws apart. In this example this overriding abutment member is provided by rivet transfer means, which will be described below.

The lower jaws 59 comprise two diametrically opposed lower jaw members 85, 86 one of which is shown in detail in FIGS. 18 and 19. Each of these jaws comprises a substantially cylindrical main body portion 87, a smaller diameter cylindrical stem 88, and a small rectangular section extension 89 in the outer end face of which is a semicylindrical groove 91. The face of the groove 91 is formed with teeth which are zig-zag in a section taken longitudinally along the groove 91, the crests and troughs of the teeth running circumferentially around the half-cylinder shape of the groove. The end of the head portion 87 remote from the groove 91 is provided with an inclined face 92.

The two lower jaws 85, 86 are received within two bores 93, 94 respectively in the jaw carrier boss, positioned below and parallel to the bore 82. The radially outer end of the bore opens onto the outside of the boss, the bore being of such a diameter to accommodate the body portion 87 of the jaw with a sliding fit. The radially innermost end of each bore is reduced in diameter to receive the stem portion 88 of the jaws with a sliding fit. The jaws are positioned with the two semicylindrical grooves 91 superposed so that when the jaws are in a position towards each other, i.e. in their gripping position, the two sets of semi-cylindrical teeth close together to grip the grooved tail-most portion of the mandrel between them. Each jaw is urged radially outwards, i.e. away from its gripping position, by means of a helical compression spring 95 surrounding the stem portion 88 of the jaw and acting between the inner end wall of the bore and the annular shoulder between the body portion 87 and the stem portion 88 of the jaw.

The inclined sloping face 92 of each jaw member projects outside the jaw carrier boss 71, and is in contact with the inclined face 96 of a jaw actuating cam 97. The two jaw actuating earns 97 are carried inside the upper part of a cylindrical extension 98 of a jaw actuating piston 99. This jaw actuating piston 99 is annular in shape, and works in an annular working space whose inner circumference is provided by the outer cylindrical surface of the jaw carrier boss 71 and whose outer cylindrical surface is provided by a cylinder casing 101 secured to the jaw carrier 61 around the lower portion of the jaw carrier boss 71. The high pressure air line 37 is connected to the space within the jaw actuating cylinder below the piston 99, and the high pressure air line 36 is connected to the space above the jaw actuating piston. The inclined surface 92 of each lower jaw is urged into contact with the inclined surface 96 of the associated cam by means of the spring 95, and the arrangement is such that when the jaw actuating piston 98 is in its raised position the two lower jaws are closed so that they grip the mandrel, and when the jaw actuating piston 98 is in its lower position the two lower jaws move apart under the urging of springs to release the mandrel.

Pneumatic signalling means 104 are provided for providing a pneumatic signal indicating when the lower jaws 85, 86 are in the closed position. This takes the form of a pneumatic valve having a body attached to the jaw actuating piston 98 and a co-operating valve member carried by the top wall 102 of the cylinder 101. When the jaw actuating cylinder 98 is raised (i.e. when the lower jaws are in their gripping position) the valve member is withdrawn from the valve body so that the valve is open. This connects a signal conduit 105 to a low pressure air supply conduit 103, thus providing a low pressure air signal to the control gear. When the valve actuating piston 98 is lowered (i.e. when the jaws are not in their gripping position) the valve member enters the valve body and closes the valve, thus cutting off the pneumatic signal along conduit 105.

The riveting apparatus of this example also includes rivet transfer means for repeatedly transferring rivets one at a time from the lower end of the rivet feed tube 28 onto the upper or tail end of the mandrel 40. Formed integrally with the upper end of the jaw carrier boss 71 and projecting upwardly therefrom are two diametrically opposed arms 106, 107. Secured to the upper ends of these arms is a yoke bracket 108 extending transversely to one side of the arms. Secured to the corresponding side of the upper bracket 43 is another bracket 109 which extends downward towards the bottom bracket 42 and is positioned within the yoke bracket 108. The lowermost portion of the bracket 109 is substantially triangular, as illustrated in FIGS. 4 and 8. The lowermost part of the rivet feed tube 28 enters the top of the bracket 109 through a slot 114 through the upper end of the bracket 109 and the upper frame bracket 43, and extends downwardly through another inclined slot 115 in the lower portion of the bracket 109. The bottom end 116 of the feed tube 28 faces downwardly and is immediately above a small pocket 117 (see FIGS. 4 and 8) which is of sufficient size to contain one rivet. This pocket is triangular in section, its rear wall being provided by the wall at the narrow inner edge of the bottom part of the bracket 109,

and the other two walls being formed by adjacent end portion of two leaf springs 118, 119 which are respectively secured to two inclined faces of the bottom por-.

The rivet is pushed out of the pocket, between the two springs 118, 119, by means of a rivet shutter 121, shown in detail in FIGS. 14 and 15. The shutter has a flat cylindrical head 122 and a rectangular body section 123 having, at the end opposite the head, a V-section groove 124. One corner of the body portion is cut off by a stepped chamfer 125. The rivet shutter 121 is mounted in a bore 126 in the lower portion of the bracket 109 for reciprocation transversely of the axis of the rivet head, so that the V-groove 124 enters into the pocket 117 through a slot in the back wall thereof, the cylindrical head 122 being a sliding fit in the bore 126 behind the pocket. The upper edge face 127 of the shutter also closes the bottom end 116 of the rivet feed tube 28 when the V-groove in the shutter projects into the pocket 117 to eject a rivet therefrom. The rivet shutter 121 is urged into its retracted position (i.e..

when it does not enter the pocket) as illustrated in sufficient to clear the end of the pawl arm 132. The lowermost portion of the groove 141 has an inclined floor 142, so that the groove is shallower at its lower end, into which opens the end of the rivet shutter bore 126. As the rivet shutter mechanism descends, the pawl 129 rides up the ramp 142, against the spring 134 as will be described later.

Pneumatic signal means 175 are provided to give'a pneumatic signal indication when the shutter 121' is in the position in which it is inside the pocket 117 and is sealing the lower end of the feed tube 28. This is provided by making the head 122 of the shutter act as a valve member in a valve formed in the bore 126. When the shutter is in this position, alow pressure pneumatic supply line 177, is connected by means of a port (not shown) in the bore 126 with a signal conduit 176 which is connected to the control gear, th'ussupplying a pneumatic signal indicating that the shutter is in the full over position. When the shutter is retracted from the pocket 117, this pressure signal is not supplied to the conduit 176.

When a rivet is pushed out of the pocket 117 by means of the rivet shutter 121, it enters a rivet transporter, which will now be described.

The rivet transporter 151 is carried by the upper frame bracket 43 for vertical reciprocation in line with the mandrel axis. It comprises a plunger having a stem FIGS. 8 and 9 by a helical compression spring 128' within the bore 126. The shutter is retained in this position by means of a stop 120, which prevents the spring 128 from ejecting it completely. It also determines the retracted position os that the front V-groove face of the shutter is correctly positioned at the back of the pocket. The rivet shutter is periodically driven into the pocket 117 by means of a shutter actuating mechanism 130 which is mounted on the center of the yoke bracket l08 on the upper end of the jaw carrier boss 71. Theshutter actuating mechanism comprises a tube 138 secured to the yoke bracket 108, containing a plunger 137 which can be reciprocated in a direction parallel to the direction of movement of the rivet shutter 121. The plunger is urged towardsthe shutter by a helical compression spring 134, its inward travel being limited by adjustable lock nuts 135 on the tail of the plunger. At its radially inner end the plunger 137 carries a pawl 129 mounted on a pivot 131 for limited rotational movement in a vertical plane. The pawl is L- shaped, the longer arm 132 projectingaway from the plunger 137 towards the rivet shutter 121. The pawl arm 132 is retained in this position by means of a leaf spring 133 mounted on the plunger 137 and bearing on the underside of the pawl. However, the urging of this leaf spring can be overcome bythe application of sufficient thrust to the arm 132 of the pawl in a direction vertically downwards. When the jaw carrier 61 is in its lowermost position (as illustrated in FIG. 5) the pawl arm 132 is aligned with and inside the bore 126, its outer end being in contact with the, rivet shutter 121 to hold the shutter pushed into the pocket 1 17 against the urging of its spring 128. When the jaw carrier 61 is in its uppermost position, the rivet actuating mechanism 126 is nearer the upper bracket 43, as illustrated in FIG. 9. The arm 132 of the pawl is then received within a groove 141 in the outer face of the bracket 109. The upper portion of the groove 141 is of uniform depth 152 and a head 153 sliding within a bore 154 within the top bracket 43. The plunger is spring-urged. downwardly by means of a helical compression spring 155 around the plunger stem within the bore 154. Downward movement of the plunger is limited by adjustable locknuts 156 on the plunger stem l52 above the top bracket 43. Upward movement of the plunger is limited by contact of the top of the plunger head 153 with a shoulder 150 in the bore 154. One side of the lower part of the plunger facing the bracket 109 is inclined as shown at 158 to provide a cutaway portion to accommodate the rivet feed tube 28. Pivotally mounted in a recess 159 in theopposite face'of the lowermost part of the plunger is a transporter arm 161, illustrated in detail in FIGS. 11, 12 and 13. The lowermost half of the transporter arm, which projects below the bottom of the plunger 153, is T-shaped in cross-section. The lowermost part or nose 162 of the arm is thicker and contains on one face a pocket 163 of appropriate size and shape to receive one rivet. As illustrated in FIG. 12, the remainder of the length of the transporter arm is of uniform thickness, the face which contains the pocket 163 being joined to thispart by means of a radiussed sloping face 164. A slot passes through the pocket, to allow axial insertion and sideways removal of the mandrel 40. As illustrated in FIG. 11, the lowermost end of the transporter nose is tapered, having two inclined faces 165, 165, the angle of inclination of these faces matching the angle of inclination of the inclined faces 74 of the upper jaws of the riveting machine. The uppermost half 166 of the transporter arm, which is received within the recess 159 in the plunger, is narrower by virtue of the omission of the flanges which form the head of theT-section in the lower half of the arm. Through this part of the transporter arm passes the pivot 167 by means of which the transporter arm is pivoted to the plunger 153. As illustrated in FIG. 9, the pivot 167 is near the bottom of the plunger 153, and the recess of 159 is deeper at its upper part to allow the part of the transporter arm above the pivot 167 to pivot into the recess, so that the lower portion of the transporter arm including the pocket 163 can pivot outwardly. The top of the transporter arm is urged away from the plunger by means of a helical compression spring 168, pivoting movement of the transporter arm under the urging of this spring being limited so as to define the position of the transporter arm about its pivot, by contact of the face of the transporter arm with the lower end of the adjacent face of the plunger head 153.

When the rivet transporter is in its lowermost position (as illustrated in FIG. the pocket 163 in the transporter nose is immediately adjacent and opposite the pocket 117 at the bottom end of the rivet feed tube 28, to receive a rivet pushed out of the pocket 117 by the shutter 121. The inclined surfaces 165 of the transporter nose are nearly in contact with the faces 74 of the upper jaws (i.e. a few thousandths of an inch away).

Pneumatic signal means are provided to indicate pneumatically when the rivet transporter is in this lowermost position. This signal means is provided in the form of a pneumatic on/ofi' valve formed within the upper bracket 43. The upper portion of the plunger 153 within the bore 154 is formed with a circumferential groove 171 which, when the transporter is in its lowermost position, connects two pneumatic conduits 172 and 173 with each other, thus allowing a low pressure pneumatic signal to pass to the pneumatic control gear. When the rivet transporter moves upwardly from this position, the conduits are not connected and no pneumatic signal passes along the conduit 172.

Pneumatic signal means is also provided for giving a pneumatic indication when the head of the mandrel 40 is fully retracted into the rivet placing jaws, i.e. when the jaw carrier 61 is in its uppermost position. This is provided by a pneumatic micro switch 178 having an actuating arm 179. When the jaw carrier 61 is in its fully raised position the top of the upper wall 102 of jaw carrier 61 meets and moves the actuating arm 179, thus connecting a pneumatic signal conduit 181 to a low pressure air supply conduit 182. This feeds a low pressure air signal along the conduit 181 to the pneumatic control gear, the signal not being present when the jaw carrier is not in its uppermost position.

It will be apparent to those skilled in the art of blind riveting that the mandrel 40 must be accurately initially positioned in the riveting head in a longitudinal direction. One possible form of device for assisting in this location is illustrated schematically in FIG. 3 only. This comprises a plunger 185 mounted on an inclined axis within a bore in the top bracket 43. In its retracted position illustrated in FIG. 3 the location plunger is outside the alignment of the mandrel and the rivet feeding mechanism of the riveting head. The lower end of the plunger is formed with a suitably shaped recess such as is illustrated at 186 in FIG. 3. To insert and locate a mandrel in the riveting head, both upper and lower sets of jaws are held open and the location plunger 185 lowered until the shaped lower end is aligned with the mandrel axis and in contact with the top of the jaw carrier boss 71. The mandrel is then inserted up the barrel 54 from the lower end until the top end of the mandrel is received within the recess 186 at the bottom of the location plunger. The upper and lower jaws are then allowed to close, and the location plunger is retracted. Other means for suitably locating the mandrel on its initial insertion into the riveting head will be apparent to those skilled in the art of blind riveting.

The pneumatic control gear is illustrated schematically in FIG. 20. This pneumatic control gear will be described in outline only, the details being apparent to those skilled in the art of pneumatic control gear.

The various pneumatic signalling means 175, 104, 178 and 170 have already been described. Each of the low pressure pneumatic supply lines to them is connected to the low pressure air feed line 39, which is derived from a high pressure air supply line by means of a reduction valve and a reservoir. In addition, the control gear includes a start button 191 which, when depressed against a spring, momentarily opens a pneumatic on/off start valve 192, thus sending a low pressure air signal along a conduit 193. This is arranged to initiate a cycle of the riveting machine. The pneumatic control gear includes a pneumatic logic circuit 194 incorporating a number of turbulence amplifiers. The construction and operation of this logic circuit forms no part of the present invention, and will not be described further in the present specification. The design, construction and operation of a suitable pneumatic logic system would present no difficulty to those skilled in the art. The outputs of the four pneumatic signalling means previously described, and that of the pneumatic start switch 192, are fed into the pneumatic logic circuit 194. This logic circuit has two low pressure outputs, 195, 196 respectively. The low pressure output 195 is connected to control a low pressure/high pressure pneumatic relay 197, and similarly the low pressure output 196 is connected to control a low pres sure/high pressure pneumatic relay 198. The high pressure input side-of each relay 197 and 198 is connected to the high pressure air supply line 33. The high pressure output of the relay 197 is connected by means of high pressure conduit 199 to a high pressure pneumatic four-way spool valve 201. The high pressure input of the valve 201 is connected to the high pressure air supply line 33, and the two high pressure lines 36 and 37 are connected respectively to the two outputs of the valve 201. The relay 197 and four-way valve 201 are arranged so that, when a low pressure air signal appears in the output 195, the relay 197 actuates the valve 201 to supply high pressure air to the line 36 whilst venting the line 37 to atmosphere, thus allowing the lower jaws 59 to open under the urging of their springs 95 to release the mandrel. Similarly, when no low pressure air signal appears at the output 195, the relay 197 controls the valve 201 to supply high pressure air to the line 37 whilst venting the line 36 to atmosphere, thus closing the lower jaws to their gripping position. The other relay 198 is connected by means of high pressure conduit 202 to control the second high pressure pneumatic four-way spool valve 203, which has its high pressure input connected to the high pressure air supply line 33 and its two outputs connected respectively to the high pressure lines 34 and 35 controlling the movement of the jaw carrier 61 and thus of the mandrel 40. The arrangement is such that when a low pressure air signal appears at the output 196 the relay 198 controls the valve 203 to supply high pressure air to the line 35 whilst venting the line 34 to atmosphere, thus moving the jaw carrier fully upwards, i.e. retracting the mandrel head into the placing jaws 56, 57. Likewise, when no low pressure air signal appears at the output 196, the relay 198 controls the valve 203 to supply high pressure air to the line 34 whilst venting the line 35 to atmosphere, thus moving the jaw carrier 61 to its fully downward position i.e. with the mandrel head protruding fully from the riveting jaws.

The arrangement of the various pneumatic signalling means and of the pneumatic logic circuit 194 is such that theriveting apparatus is in a stable condition when all four of the following parts of the machine are respectively in the positions indicated: 7

i. the rivet transporter is in the fully downward position;

ii. the jaw carrier and mandrel are in the lowermost position;

iii. the lower jaws are in their gripping position;

iv. the rivet shutter is in the full over position inside the pocket 117. In this stable condition, no pneumatic signal appears at either output 195, 196. This position is illustrated in FIGS. 3, 4 and 5. A riveting cycle is then initiated by momentary depression of the start button 191, as previously mentioned. The cycle then takes place automatically, the pneumatic signals generated by the various signalling means actuating the pneumatic circuit to control the movement of the lower jaws and of the jaw carrier automatically, as will be described below.

When the riveting machine is in operation, a column of rivets on the mandrel occupies the whole of the length of the mandrel from top to bottom, so that thrust applied to the uppermost rivet by the lower jaws 59 is transmitted to the lowermost rivet above the rivet placing jaws, to force that rivet through the jaws, as previously described. It will be assumed in the following description that such a full column of rivets is in position on the mandrel. The column of rivets is not depicted in the accompanying drawings, for reasons of ease and clarity of illustration.

When the machine is in operation and is in the stable or starting position, there is one rivet at the bottom end of the mandrel below the jaws 56, 57, held between those jaws and the mandrel head 48. When the riveting cycle is initiated by pressure on the start button 191, the pneumatic logic circuit 194 produces a signal at the output 196, thus causing the jaw carrier to move upwards. This pulls the mandrel head 48 through the rivet, thus expanding the tail of the rivet to form a blind head and placing the rivet in whatever suitable apertured workpiece the rivet and mandrel head have been previously inserted into.

At the start of the cycle, a rivet is held in the pocket 163 in the transporter nose 162. This rivet has been inserted in the pocket 163 by the action of the rivet shutter during the previous riveting cycle. As the jaw carrier 61 rises the inclined faces 74 of the upper jaws meet the inclined faces 165 on the bottom of the transporter nose. As the thrust on the transporter arm is in a line passing through its pivot, the arm does not rotate about its pivot. The geometry of the inclined faces, and relative strengths of the upper jaw springs 83 and the transporter plunger spring 155, is such that the rising jaws force the rivet transporter upwards, compressing the spring 155, until the top of the plunger head 153 meets the shoulder within the bore 154. This occurs well before the jaw carrier has reached its uppermost position. Continuing upward movement of the jaw carrier makes the inclined surfaces at the bottom end of the transporter nose force the upper jaws apart. When this happens, the transporter plunger spring is released and the transporter moves down under the urging of its spring 155 to return to its lowermost position, determined by the adjustable lock nuts 156, feeding the rivet in its pocket 163 on to the tail end of the mandrel. The spring-loaded upper jaws close behind the transporter nose as soon as it has passed them. Meanwhile the jaw carrier 61 is still rising. The lower jaws then meet the bottom end of the rivet transporter nose and, as the jaw carrier continues to rise, they force the rivet transporter upwards again, compressing its spring 155. This continues until the jaw carrier 61 reaches its uppermost position, by which time the rivet transporter has not reached its fully uppermost position determined by the shoulder 150.

Meanwhile, as the jaw carrier 61 has been rising, it has carried the shutter actuating mechanism 130 with it. Since the projecting arm 132 of the pawl 129 is held by the upper outer end of the bore 126, the pawl is forced to rotate about its pivot 131 against the urging of the leaf spring 133. Thus the pawl arm 132 withdraws from the bore 126, allowing the rivet shutter 121 to move under the urging of its spring 128 outwardly to stop 120. This allows a further rivet to drop from the bottom of the feed tube 28 into the pocket 1 17. As the shutter actuating mechanism 126 continues to rise, the pawl arm 132 rides along the inclined floor 142 of the groove 141 and progressively returns to its previous alignment under the urging of the spring 133.

When the jaw carrier 61 reaches its uppermost posi tion, the pneumatic signalling switch 178 is actuated to pass a pneumatic signal to the logic circuit 194. The arrangement of the logic circuit is such that this produces a pneumatic signal at the output 195, causing the lower jaws to be opened. Thisallows the rivet transporter to move downwardly again under the urging of its spring 155, carrying with it the rivet which is still retained in its pocket 163 and is riding on the mandrel. FIG. 6 shows the transporter nose passing through the lower jaws. When the rivet transporter reaches its fully downward position, the pneumatic signalling device transmits a pneumatic signal. The signalling device 178 is still transmitting a pneumatic signal, whilst the signalling device 104 is not transmitting a signal, since the lower jaws are now open. In these conditions the logic circuit 194 removes the pneumatic signal from the output 195, thus causing the lower jaws to be closed. This position is shown in FIGS. 7, 8 and 9. It should be noted that, since the upper jaws have automatically closed behind the rivet transporter when it passed through them they have been gripping the mandrel for the whole time the lower jaws have been open. The closure of the lower jaws causes the pneumatic signalling device 104 to again transmit a signal to the logic circuit 194. The arrangement of the logic circuit is such that it now removes the signal from the output 196, thus causing the jaw carrier and jaws to move downwardly again. The lower faces of the lower jaws meet the curved portion 164 of the-rivet transporter arm just above the nose, and as they move downwardly the curved portion rides on them so that the rivet transporter arm 161 is forced aside, rotating about its pivot 167 against the action of its spring 168. The rivet which was held in the pocket 163 is thus left at the top of the column of rivets on the mandrel. The descending lower jaws contact this rivet and move the column of rivets downwards, forcing the lowermost rivet through the riveting jaws ready for the next placing cycle. At the same time, as the jaw carrier 61 descends, the shutter actuating mechanism 126 also descends with it. The pawl 129 rides along the inclined portion 142 of the floor of the groove 141, forcing the plunger 137 outwards and compressing the spring 134. This continues until the jaw carrier 61 reaches its lowermost position, when the pawl 129 reaches the bottom end of the ramp 142 and falls into the bore 126. Since the spring 134 on the plunger is stronger than the spring 128 on the rivet shutter, the pawl forces the rivet shutter inwards again, thus transferring the rivet which is in the pocket 117 into the pocket 163 in the rivettransporter arm. This completes the placing cycle, all the parts of the mechanism now having returned to their initial stable position.

It will be apparent that, when starting the riveting machine, rivets are fed onto the mandrel without being placed through the placing jaws 56, 57 until the column of rivets on the mandrel is complete. As explained placing of rivets commences only when the mandrel is full of rivets and the thrust exerted on the uppermost rivet by the lower jaws moving downwards forces the lowermost rivet through the placing jaws.

The riveting apparatus described in the foregoing example is advantageous in a number of ways. In previous riveting apparatus in which a plurality of tubular rivets have been loaded onto a mandrel for successive blind placing, the maximum number of rivets per loading has been limited by the length of the mandrel. It was necessary to remove the mandrel from the machine when all the rivets on the mandrel had been placed and to load a further column of rivets onto the mandrel over its tail end, and then replace the mandrel in the riveting apparatus. The riveting apparatus which has been described in the foregoing example enables the rivets to be repeatedly fed onto the mandrel over its tail end, thus enabling riveting to take place continuously without periodic removal of the mandrel for reloading. Furthermore, in the example described above, the riveting jaws 56, 57 are fixed with respect to the main frame of the machine, and the mandrel reciprocates relatively to the jaws. In previous apparatus, the mandrel had been fixed with respect to the main body of the machine and the riveting jaws and barrel have reciprocated with respect to the mandrel, thus causing oscillation of the riveting machine at the moment of placing of each rivet which may be undesirable.

FIG. 21 illustrates a modification of the upper and lower jaws and the jaw actuating mechanism (the mandrel and the rivet transfer mechanism are omitted from FIG. 21 for clarity of illustration). The construction and operation of the jaw mechanism of this modification are substantially similar to those of the example described above, with the exception that means is provided for altering the thrust on the springmrged upper jaws in synchronism with the opening of those jaws by the rivet transporter arm. As illustrated in FIG. 21, each upper jaw 201 is urged into its gripping position by means of a helical compression spring 202. The rear end of the compression spring is seated on a back-up member 203 which has an inclined rear face 204 and is reciprocable by means of the upper inclined face 205 of a double-slope cam 206. The lower inclined face 207 of the cam 206 actuates one of the lower jaws 208 in a manner similar to that described in the example above, except that the direction of inclination of the lower jaw cam faces is reversed. Thus the lower jaws are closed when the jaw actuating piston 209 is lowered with respect to the jaw carrier body 211. Similarly the spring pressure urging the upper jaws closed is increased when the lower jaws are released (to assist in gripping the mandrel tightly) and is reduced when the lower jaws are in their gripping position (thereby assisting the easy opening of the upper jaws by the rivet transporter arm).

The invention is not restricted to the details of the foregoing example and modification thereof. For instance, although in the above example the riveting head is mounted in a vertical position to place rivets vertically downwards from above, it may be pointed in any direction desired, and may if desired be mounted on an adjustable stand. The functioning of the apparatus does not rely upon gravity (apart from the uppermost part of the rivet feed tube 28 above the air pusher 29).

The sequential releasing and gripping of the sets of jaws may be actuated and controlled in other ways. For example, instead of the upper jaws being spring loaded to grip the mandrel they may be completely positively driven to do so.

We claim:

1. Riveting apparatus comprising an elongate mandrel having a head end and a tail end and a radially enlarged head at the head end, the mandrel carrying, in use, a plurality of tubular rivets; a plurality of disengageable holding means arranged to hold the mandrel at positions spaced apart along the length thereof, at least one of said holding means being movable while holding the mandrel to pull the head through each of said rivets in turn, each of the holding means being disengageable from the mandrel in turn; the arrangements being such that a rivet may be fed on to the mandrel at the tail end thereof remote from the mandrel head and moved along the mandrel, past the holding position of each holding means while the latter is disengaged, the mandrel being held, at any one instant, by at least one of said holding means.

2. Riveting apparatus comprising an elongate mandrel having a head end and a tail end and a radially enlarged head at the head end, the mandrel carrying, in use, a plurality of tubular rivets; a plurality of retractable gripping means arranged to grip the mandrel at gripping positions spaced apart along the length thereof, said gripping means being movable while gripping the mandrel to pull the head through each of said rivets in turn, and means for successively retracting from the mandrel each of the gripping means in turn; the arrangement being such that a rivet may be fed on to the mandrel at the tail end thereof remote from the mandrel head and moved along the mandrel, past the gripping position of each gripping means while the latter is retracted, the mandrel being gripped, at any one instant, by at least one of the gripping means. 

1. Riveting apparatus comprising an elongate mandrel having a head end and a tail end and a radially enlarged head at the head end, the mandrel carrying, in use, a plurality of tubular rivets; a plurality of disengageable holding means arranged to hold the mandrel at positions spaced apart along the length thereof, at least one of said holding means being movable while holding the mandrel to pull the head through each of said rivets in turn, each of the holding means being disengageable from the mandrel in turn; the arrangements being such that a rivet may be fed on to the mandrel at the tail end thereof remote from the mandrel head and moved along the mandrel, past the holding position of each holding means while the latter is disengaged, the mandrel being held, at any one instant, by at least one of said holding means.
 1. Riveting apparatus comprising an elongate mandrel having a head end and a tail end and a radially enlarged head at the head end, the mandrel carrying, in use, a plurality of tubular rivets; a plurality of disengageable holding means arranged to hold the mandrel at positions spaced apart along the length thereof, at least one of said holding means being movable while holding the mandrel to pull the head through each of said rivets in turn, each of the holding means being disengageable from the mandrel in turn; the arrangements being such that a rivet may be fed on to the mandrel at the tail end thereof remote from the mandrel head and moved along the mandrel, past the holding position of each holding means while the latter is disengaged, the mandrel being held, at any one instant, by at least one of said holding means.
 2. Riveting apparatus comprising an elongate mandrel having a head end and a tail end and a radially enlarged head at the head end, the mandrel carrying, in use, a plurality of tubular rivets; a plurality of retractable gripping means arranged to grip the mandrel at gripping positions spaced apart along the length thereof, said gripping means being movable while gripping the mandrel to pull the head through each of said rivets in turn, and means for successively retracting from the mandrel each of the gripping means in turn; the arrangement being such that a rivet may be fed on to the mandrel at the tail end thereof remote from the mandrel head and moved along the mandrel, past the gripping position of each gripping means while the latter is retracted, the mandrel being gripped, at any one instant, by at least one of the gripping means.
 3. Riveting apparatus as claimed in claim 2, in which the gripping positions are near the tail end of the mandrel.
 4. Riveting apparatus as claimed in claim 2, in which there are two gripping means.
 5. Riveting apparatus as claimed in claim 2, in which each gripping means comprises a plurality of jaws which are urged together to grip the mandrel between them.
 6. Riveting apparatus as claimed in claim 5, in which each gripping means comprises two jaws.
 7. Riveting apparatus as claimed in claim 2, in which at least one of the gripping means includes resilient urging means urging it either to grip, or to retract from, the mandrel, and in which the apparatus also includes override means for overriding the resilient urging means and positively driving the gripping means to retract from, or to grip, as the case may be, the mandrel.
 8. Riveting apparatus as claimed in claim 7, in which one of the gripping means includes such resilient urging means urging it to grip the mandrel, and another of the gripping means includes such resilient urging means urging it to retract from the mandrel.
 9. Riveting apparatus as claimed in claim 2, which includes rivet transfer means for transferring rivets in succession from a rivet supplying device onto the aforesaid tail end of the mandrel.
 10. Riveting apparatus as claimed in claim 9, in which the rivet transfer means is also arranged to convey the said rivets in succession along the mandrel past at least one of the gripping means.
 11. Riveting apparatus as claimed in claim 10, in which the rivet transfer means is arranged to convey rivets in succession along the mandrel past all of the gripping means.
 12. Riveting apparatus as claimed in claim 2, in which the rivet transfer means is movable lengthwise of the mandrel at least as far as one of the gripping means, and arrival of the rivet transfer means at said one gripping means actuates retraction of the said one gripping means.
 13. Riveting apparatus as claimed in claim 12, in which the said one of the gripping means includes resilient urging means urging it to grip the mandrel and in which arrival of the rivet transfer means at the said one gripping means overrides the resilient urging means and drives the said one gripping means to retract from the mandrel. 